Determination of some herbicide residues in sweet potato

Abstract

The use of herbicides in weed control is on the increase but such chemical residues in crop plants mostly cause health risks. The objective of this work was to determine the level of some herbicide residues in sweet potato. The sweet potatoes were cultivated in randomized complete block design (RCBD) with four replications at the Crops Research Institute Agronomy fields, Kwadaso, Ghana. The different treatments made up of combinations of five pre-emergence herbicides (butachlor [50 g/L—3 L/Ha], imazethapyr [240 g/L—3 L/Ha], metolachlor [333 g/L—4 L/Ha], pendimethalin [500 g/L—3 L/Ha] and terbutryn [167 g/L—4 L/Ha]) and one (1) post-emergence herbicide (propaquizafop [100 g/L—1.2 L/Ha]) were applied. After harvest, samples were randomly selected and extracted using a modified QuEChERS extraction method followed by liquid chromatography-mass spectrometry (LC-MS) to determine the residual levels of the herbicides. The results showed that butachlor, imazethapyr, terbutryn and propaquizafop were not detected in their respective sweet potato samples analysed. However, pendimethalin and metolachlor residues were detected at concentrations of 0.0023 µg/g and 0.0029 µg/g, respectively. The findings suggest that the herbicide residue levels detected were considerably lower than the maximum acceptable limit (0.05 µg/g) and thus the application of these pre-, and post-emergence herbicides at the recommended rates in sweet potato is safe from the residual point of view.